The applicant, a participant in the current Herpetic Eye Disease Study (HEDS), proposes to be a Regional Center for Phase II of the Herpetic Eye Disease Study. Phase II will consist of two randomized, double-masked clinical trials and a non-experimental study of triggers of recurrence of ocular herpetic disease. The first trial, HEDS-EKT, will compare acyclovir to placebo for the prevention or delay of subsequent stromal keratitis or iritis in patients with active herpetic epithelial keratitis. The second, HEDS-APT, will compare acyclovir to placebo for prolonging time to recurrence of herpetic eye disease in patients with an episode of any herpetic eye disease in the past year and who have been free of disease and off all treatment for the past month. The triggers study will obtain data by questionnaire on stress, trauma, and other potential triggers of recurrence of herpetic disease for correlation with recurrence data from the two clinical trials. As a Regional Center, the applicant will be responsible for entering patients in the two clinical trials, and treating and following them according to protocol; entering consenting randomized patients into the triggers study; coordinating and overseeing the participation of 7 additional participating local sites in the APT and EKT trials; and participating in the governance of HEDS via participation on the Executive Committee.